1. Field of the Invention
The present invention relates generally to paint spray guns of the type including atomizing or swirl valves seated within an outlet chamber of a paint pump subassembly. In particular, the present invention relates to a paint spray gun with a swirl valve having an elastomer seat-engaging surface integrally molded therewith.
2. Description of the Related Art
Airless paint spray guns, also sometimes known as cup guns, are generally known and in widespread use. Spray guns of this type are commercially available from Wagner Spray Tech corporation of Minneapolis Minn., the assignee of the present invention, and are disclosed in the Wagner U.S. Pat. No. 3,899,134 and the Soderlind et al. U.S. Pat. No. 4,036,438. These spray guns include a paint cup or container that is releasably mounted to a portable gun assembly which includes a pump subassembly and a spray tip. The gun assembly includes a handle with a trigger-type on/off switch, and a motor for driving a piston in the pump subassembly.
Pump subassemblies of the type shown in the Soderlind et al. patent referred to above include a pumping chamber connected to and supplying an outlet chamber. The piston is reciprocatingly driven within the pumping chamber by a linear motor. The pumping chamber is preferably fabricated of aluminum, stainless steel or another relatively hard and corrosion resistant metal. A replaceable poppet valve member is lightly spring biased into engagement with a valve seat at the inlet to the outlet chamber. A replaceable swirl valve having a beveled surface is located at a discharge end of the outlet chamber and is positioned adjacent an atomizing spray tip, with the beveled surface of the swirl valve engaging a beveled seat at an outlet of the outlet chamber to form a paint-tight seal between the swirl valve and the seat at the discharge end of the outlet chamber. A number of paint swirl apertures extend through the swirl valve to permit transmission of paint or other material to be sprayed from the outlet chamber to the spray tip. In such prior art guns, the swirl valve was fabricated from a polymer such as nylon. When the spray gun is turned on by actuating the trigger, the motor drives the piston in the pump subassembly to draw paint from the container into the pumping chamber and thereafter move it to the outlet chamber where the paint is forced through the swirl valve apertures at high pressure and allowed to exit the gun via the atomizing spray tip, forming an atomized spray which may be directed to a surface desired to be painted by the operator of the gun.
Along with other parts which have been in contact with paint during operation, the swirl valve is typically removed and cleaned after each use of the spray gun. During reassembly, if the nut holding the spray tip is not tightly screwed onto the pump assembly and the swirl valve properly seated in the discharge end of the outlet chamber before the spray gun is reused, the high pressures developed within the outlet chamber of the pump subassembly can cause paint to get between the surfaces of the swirl valve and the seat at the discharge end of the outlet chamber. If allowed to continue for a substantial length of time, erosion of the swirl valve resulting in uneven and sputtering paint spray can occur as a result. The swirl valve must then be replaced to restore proper operation of the spray gun.
There is, therefore, a continuing need for improved airless paint spray guns. In particular, there is a need for a spray gun having reduced susceptibility to sputtering caused by the swirl valve erosion that occurs in known spray guns. The swirl valve should of course be efficient to manufacture and be easily cleanable after use. The ability to easily and efficiently retrofit existing spray guns is especially desirable.